1. The Field of the Invention
The present invention generally relates to a high-strength binder material for forming drilling tools and other tools that may be used to drill subterranean formations.
2. Discussion of the Relevant Art
Drill bits and other earth-boring tools are often used to drill holes in rock and other hard formations for exploration or other purposes. The body of these tools is commonly formed of a matrix that contains a powdered hard particulate material, such as tungsten carbide. This material is typically infiltrated with a binder, such as a copper alloy, to bind the hard particulate material together into a solid form. Finally, the cutting portion of these tools typically includes an abrasive cutting media, such as for example, natural or synthetic diamonds.
To form the body, the powdered hard particulate material is placed in a mold of suitable shape. The binder is typically placed on top of the powdered hard particulate material. The binder and the powdered hard particulate material are then heated in a furnace to a flow or infiltration temperature of the binder so that the binder alloy can bond to the grains of powdered hard particulate material. Infiltration can occur when the molten binder alloy flows through the spaces between the powdered hard particulate material grains by means of capillary action. When cooled, the powdered hard particulate material matrix and the binder form a hard, durable, strong body. Typically, natural or synthetic diamonds are inserted into the mold prior to heating the matrix/binder mixture, while PDC inserts can be brazed to the finished body.
The compositions of the matrix and binder are often selected to optimize a number of different properties of the finished body. These properties can include transverse rupture strength (TRS), toughness, tensile strength, and hardness. One important property of the binder is the binder's infiltration temperature, or the temperature at which molten binder will flow in and around the powdered hard particulate material. The chemical stability of the diamonds is inversely related to the duration of heating of the diamonds and the temperature to which the diamonds are heated as the body is formed. Thus, when forming diamond drilling tools, it is desirable to use a binder with a low enough infiltration temperature to avoid diamond degradation.
Binder alloys with low infiltration temperatures are known in the art; however, such binders often sacrifice one or more of tensile strength, hardness, and other desirable properties at the expense of a lower infiltration temperature. For example, many conventional copper-tin alloys have a low infiltration temperature, but also have relatively low tensile strength. On the other hand, many conventional copper-zinc-nickel alloys have a low infiltration temperature with a relatively high tensile strength, but also have a relatively low hardness.
In some cases, drilling tools may be expensive and their replacement may be time consuming, costly, as well as dangerous. For example, the replacement of a drill bit requires removing (or tripping out) the entire drill string from a hole that has been drilled (the borehole). Each section of the drill rod must be sequentially removed from the borehole. Once the drill bit is replaced, the entire drill string must be assembled section by section, and then tripped back into the borehole. Depending on the depth of the hole and the characteristics of the materials being drilled, this process may need to be repeated multiple times for a single borehole. Thus, one will appreciate that the more times a drill bit or other drilling tool needs to be replaced, the greater the time and cost required to perform a drilling operation.
Accordingly, there are a number of disadvantages in conventional drilling tools that can be addressed.